Analysis of factors influencing target PASI responses and side effects of methotrexate monotherapy in plaque psoriasis: a multicenter study of 1521 patients.

Methotrexate (MTX) is commonly used as first-line systemic treatment agent in psoriasis. We aimed to evaluate the clinical characteristics and treatment responses of patients with psoriasis undergoing MTX monotherapy. Data from adult patients with plaque psoriasis who received MTX monotherapy for at least 3 months between April 2012 and April 2022 were retrospectively evaluated in 19 tertiary care centers. Our study included 722 female and 799 male patients, a total of 1521 participants. The average age of the patients was 44.3 ± 15.5 years. Mode of treatment was oral in 20.4% of patients while in 79.4% it was subcutaneous. The median treatment duration was 8 months (IQR = 5-15). The median weekly dose was 15 mg (IQR = 11-15). 1448 (95.2%) patients were taking folic acid supplementation. At week 12, 16.3% of the patients achieved PASI (Psoriasis Area and Severity Index) 90 response while at week 24, 37.3% achieved it. Logistic regression analysis for week 12 identified the following independent factors affecting PASI 90 achievement positively: median weekly MTX dose ≤ 15 mg (P = 0.011), subcutaneous administration (P = 0.005), no prior systemic treatment (< 0.001) and folic acid use (0.021). In logistic regression analysis for week 24; median weekly MTX dose ≤ 15 mg (P = 0.001), baseline PASI ≥ 10 (P < 0.001), no prior systemic treatment (P < 0.004), folic acid use (P = 0.001) and absence of comorbidities (P = 0.009) were determined as independent factors affecting the achievement of PASI 90. Adverse effects were observed in 38.8% of the patients, with nausea/vomiting (23.9%) and transaminase elevation (13%) being the most common. The most common reasons for interruptions (15.3%) and discontinuations (27.1%) of the treatment were patient related individual factors. The use of MTX as the first systemic treatment agent, at doses ≤ 15 mg/week and concurrent folic acid application are positive predictive factors for achieving the target PASI response both at weeks 12 and 24. In our study, which is one of the most comprehensive studies on MTX treatment in psoriasis, we observed that MTX is an effective and safe treatment option.